Abstract: | Contributions to the Chemistry of Organo Transition Metal Compounds. 55. Preparation and Properties of Niobocenium and Tantalocenium Salts — Crystal and Molecular Structure of [(C5H5)2NbCl2][BF4] · CH3CN Niobocenium and tantalocenium compounds of the type [(C5H5)2MCl2]X (X = BF4, PBh4, PF6) were synthesized from the metallocene dichlorides and ferricenium salts, [(C5H5)2Fe]X, in methylene dichloride or tetrahydrofuran. With acetonitrile as solvent [(C5H5)2MCl2]X · CH3CN complexes are formed. Stable methyl compounds of the type [(C5H5)2M(CH3)2]X were obtained, when (C5H5)2Ta(CH3)2 is oxidized by means of ferricenium salts. The new complexes were characterized by elemental analysis, i. r., and 1H n.m.r. spectra. The structure of [(C5H5)2NbCl2][BF4] · CH3CN has been determined by X-ray structure analysis. The compound crystallizes in the orthorhombic space group Cmcm with a = 8.324(12), b = 19.581(13), c = 9,563(8) Å and Z = 4. The coordination geometry of the Nb atom is tetrahedrally. |